Technical Field
The present disclosure relates to a lock-up device, and particularly to a lock-up device for a torque converter, which is configured to transmit a torque from a front cover to a transmission-side member through a turbine.
Background Information
Torque converters are often equipped with a lock-up device for directly transmitting a torque from a front cover to a turbine. Such a lock-up device includes a piston, an input-side plate, a plurality of torsion springs, and an output-side plate. The piston is capable of being coupled by friction to the front cover. The input-side plate is fixed to the piston. The torsion springs are supported by the input-side plate. The output-side plate is elastically coupled through the torsion springs to the piston and the input-side plate in a rotational direction. The output-side plate is fixed to the turbine.
Additionally, as described in Japan Laid-open Patent Application Publication No. 2012-237441, there has been also proposed a so-called multi-plate lock-up device that a plurality of clutch plates are used to increase its clutch capacity.
In the lock-up device described in Japan Laid-open Patent Application Publication No. 2012-237441, a clutch portion is disposed between the front cover and the turbine. The clutch portion includes the plurality of clutch plates. A lock-up state (power transmission state) is herein made when these clutch plates are pressed in contact with each other by the piston. In this state, a torque from the front cover is transmitted through the clutch portion directly to the turbine without intervention of a torque converter body.
In the lock-up device described in Japan Laid-open Patent Application Publication No. 2012-237441, the piston is supported by one member disposed on the inner peripheral side of the piston (hereinafter referred to as “an inner peripheral side member”) and the other member disposed on the outer peripheral side of the piston (hereinafter referred to as “an outer peripheral side member”), while being axially movable with respect thereto. Additionally, the inner peripheral side member and the outer peripheral side member are fixed to the front cover. Hence, the inner peripheral side member and the outer peripheral side member are configured to be rotated in synchronization with the front cover while being fixed thereto.
An oil chamber is herein defined between the piston and both of the inner peripheral side member and the outer peripheral side member that support the piston. Hence, seal members are mounted between the piston and the inner peripheral side member and between the piston and the outer peripheral side member, respectively. Such a construction has a drawback that when the piston is rotated relatively to both of the inner peripheral side member and the outer peripheral side member that support the piston, abrasion occurs on: the piston; either or both of the inner peripheral side member and the outer peripheral side member that support the piston; and/or either or both of the seal members mounted between the piston and the inner peripheral side member and between the piston and the outer peripheral side member, respectively.